This is an archived article that was published on sltrib.com in 2012, and information in the article may be outdated. It is provided only for personal research purposes and may not be reprinted.

On Oct. 5, the U.S. Bureau of Labor Statistics reported the unemployment rate had dropped from 8.1 percent to 7.8 percent in September. The report couldn't have come at a better time for President Obama. In the aftermath of a shellacking in the first presidential debate, here was positive economic news.

For some, though, the timing between the dismal debate and the unemployment numbers seemed too good to be true. Jack Welch, former CEO of General Electric, smelled a conspiracy and tweeted, "Unbelievable jobs numbers ... these Chicago guys will do anything ... can't debate so change numbers."

Conservatives from Steve Forbes to Newt Gingrich rushed to Welch's defense. Since this conspiracy theory involves manipulating the aftermath of the presidential debate by way of unemployment numbers, let's call these conspiracy theorists the "aftermath-ers."

Conspiracy theories are funny things. On the one hand, they're almost universally ridiculed as paranoid fantasies. On the other hand, history is replete with examples where conspiracies did in fact play out (think Watergate). So here's the question: How do we distinguish conspiracy theories that should be given some credence from those which should be dismissed as bogus?

Conspiracy theories are rooted in skepticism  skepticism of official stories, skepticism of people in power, skepticism of others' intentions. The challenge of distinguishing credible conspiracy theories from false ones, then, is the challenge of distinguishing legitimate skepticism from illegitimate skepticism.

Brian Keeley, a philosopher, and Michael Shermer, founding publisher of Skeptic magazine, both point to radical skepticism as one version of illegitimate skepticism. If a conspiracy theory requires believing a very large number of people are all conspiring and keeping their conspiracy secret, then that's a good sign that radical skepticism is at play and the conspiracy theory is bogus.

Let me add another form of illegitimate skepticism: selective skepticism. If the evidence for a conspiracy theory arises from picking and choosing which data points from a source are suspicious, then that's a good sign that selective skepticism is at play and the conspiracy theory is bogus.

How does the "atermath-ers' " conspiracy theory hold up? To judge, we must understand how the Bureau of Labor Statistics generates its employment/unemployment numbers each month. Two surveys are conducted monthly: the Current Population Survey and the Current Employment Statistics survey. There are approximately 60,000 households included in the CPS, and every month 2,200 Census Bureau employees interview individuals from the 60,000 households in order to determine their participation in the labor force. There are approximately 141,000 businesses and government agencies included in the CES, and every month administrators from those businesses/agencies self-report their data.

The Bureau of Labor Statistics has been collecting this data for decades; the CPS, for example, has been collected every month since 1940.

The "aftermath-ers' " conspiracy theory involves both radical skepticism and selective skepticism. It involves radical skepticism because conspiring to manipulate the employment/unemployment numbers means conspiring to manipulate the CPS and the CES, and that means a conspiracy of at least 2,200 federal employees and 141,000 business/agencies  all conspiring, all keeping their conspiracy secret. It involves selective skepticism because the conspiracy theory fixates on a single data point from the Bureau of Labor Statistics (the drop to 7.8 percent). The bureau has been reporting the unemployment rate every month for decades. During the Obama administration, it peaked at 10 percent in late 2009. Where were the tweets of conspiracy then?

The "Aftermath-ers' " conspiracy theory involves both radical skepticism and selective skepticism. And that's a good sign the conspiracy theory is bogus.

James Tabery is a professor in the Department of Philosophy at the University of Utah. tabery@philosophy.utah.edu.